KR20120079978A - A space vector pwm overmodulation control method and apparatus thereof - Google Patents

Abstract

PURPOSE: A space voltage PMW(Pulse Width Modulation) over modulation control method and apparatus are provided to maximize voltage availability ratio of an SVPWM(Space Vector Pulse Width Modulation) inverter by linearizing an output voltage in an over modulation region of space vector PWM. CONSTITUTION: A commanded voltage vector transform unit(520) changes a commanded voltage into a space vector. A space vector display unit(530) is expressed as a hexagon form. A modulation index generating unit(540) obtains a modulation index by using the size of a fundamental wave component of a phase voltage and the size of a fundamental wave component of the commanded voltage. An over modulation region decision unit(550) determines a first over modulation region and a second over modulation region according to the size of the modulation index. An over modulation controller(560) calculates a section which is reflected into a basis vector model according to a hold angle.

Description

A Space Vector PWM Overmodulation control Method and Apparatus

The present invention relates to a space voltage PWM overmodulation method and apparatus thereof, and more particularly, to apply a phase overmodulation technique, a dynamic overmodulation method, to a static overmodulation technique to facilitate a command voltage in an overmodulation region of a space vector PWM. The present invention relates to a space voltage PWM overmodulation method and apparatus using an overmodulation technique that can be controlled in a simple manner.

Recently, the drive system of the motor can control the output frequency and voltage simultaneously using switching elements such as IGBT and MOSFET to enable fast switching, and generate three-phase AC output voltage from DC input power. Voltage Fed Pulse Width Modulation (PWM) inverters are used. In particular, three-phase voltage PWM inverters are widely used in motor driving and uninterruptible power supplies (UPS).

In addition, recently, various types of PWM inverters have been utilized in many fields such as high-performance electric motors, and various PWM methods for generating accurate and stable output voltages have been studied. Among the voltage modulation methods, Space Vector PWM (SVPWM) method has a fixed switching frequency and can use the DC voltage as much as possible and can suppress the harmonic components in the steady state more than other PWM methods.

The implementation of the SVPWM method is that the digital implementation method that directly calculates the application time of the gate pulse has good harmonic characteristics, fixed switching frequency and ease of implementation, and the harmonics included in the load current when the modulated output voltage is applied. It has the advantage of being less than other types of voltage modulation.

Voltage-type inverters can be produced relatively accurately by various voltage modulation methods with the command voltage given the command voltage (V ^* ) within the range of the output possible. In the overmodulation region where the command voltage (V ^* ) is out of the hexagonal inscribed circle, that is, out of the range that the inverter can linearly output, the overmodulation technique is used to limit the inverter's output voltage to the hexagonal side.

When the overmodulation occurs, the output voltage is smaller than the command voltage (V ^* ) in the overmodulation region, thereby breaking the linearity of the output voltage with respect to the command voltage. As a result, the performance of the control to control the voltage can be severely distorted, and harmonics can also occur that can degrade the overall performance of the system. Therefore, it should allow into the output voltage limit of the reference voltage inverter via the right and modulation scheme limits (for SVPWM within the hexagonal sides), or can average the reference voltage V ^* and the voltage equal to the output, the last of these and modulation scheme Much research is being done on this.

Therefore, the problem to be solved by the present invention is easy to static and modulation by using the same phase over-modulation technique used in the vector control method to easily generate the command voltage value in the static over-modulation technique of the spatial vector PWM over-modulation technique The present invention provides a spatial voltage PWM overmodulation control method and apparatus.

According to an embodiment of the present invention for solving this problem, a three-phase AC power is input to the switching element through the inductor, the switching element is turned on / off according to the feedback signal of the feedback control unit using a signal of the DC terminal AC An overmodulation control method of a three-phase voltage PWM inverter for converting a power source into a direct current power source, the method comprising: generating a command voltage for controlling switching of the switching element and converting the command voltage into a space vector, expressed in a hexagonal shape And displaying a spatial vector of the reference voltage in a fundamental vector model on a dq plane including six effective vectors facing six vertices from the center, the magnitude of the fundamental wave component of the phase voltage and the fundamental wave component of the reference voltage. Obtaining a modulation index (m) using the magnitude of the first and second modulation regions according to the magnitude of the modulation index. Determining a set region; if the first overmodulated region, the command voltage is boosted to a first reference voltage vector, and the first reference voltage vector is out of the basic vector model. Calculating a new switching time of the two effective vectors adjacent to the command voltage, and if the second overmodulation area, boosts the magnitude of the command voltage to a second reference voltage vector and maintains the holding angle α _h . Calculating and calculating a section projecting the basic vector model according to the holding angle α _h .

The step of obtaining the modulation index (m) can be obtained through the following equation.

는 상 전압의 기본파 성분의 크기를 나타낸다. Here, the command voltage (V ₁ ^* ) represents the magnitude of the fundamental wave component of the command voltage,

Denotes the magnitude of the fundamental wave component of the phase voltage.

The determining of the first overmodulation area and the second overmodulation area may include determining the first overmodulation area when the modulation index m corresponds to a range of 0.907 <m <0.9514, and a range of 0.9514 <m <1. In this case, it may be determined as the second overmodulation area.

In the first overmodulation region, the magnitude of the command voltage may be boosted to the first reference voltage vector through the following equation.

는 상기 기본 벡터 모델의 높이를 나타내고, α_c는 상기 제1 기준 전압이 상기 기본 벡터 모델과 교차하는 지점과 상기 육각형의 이웃하는 꼭지점 사이의 각도를 나타낸다. Here, V ₁ represents the magnitude of the command voltage, V ₂ represents the magnitude of the boosted first reference voltage,

Represents the height of the basic vector model, and α _c represents the angle between the point where the first reference voltage intersects the basic vector model and the neighboring vertex of the hexagon.

The magnitude of the first reference voltage according to the magnitude of the command voltage may be calculated using the following table.

In the calculating of the new switching time, a new switching time T ₁ ^new , T ₂ ^new for generating the first reference voltage vector may be represented by the following equation.

Here, T ₁ and T ₂ represent the first switching time of two valid vectors adjacent to the command voltage for generating the command voltage, and T _S represents the total switching application time.

The magnitude of the second reference voltage is fixed to 2 / 3V _dc , and the phase of the second reference voltage according to the phase of the command voltage may be set as follows.

Here, θ 'is the phase of the second reference voltage (V _new ^* ), θ is the phase of the command voltage, α _h means the holding angle of the second reference voltage.

The holding angle α _h according to the modulation index m in the second overmodulation region may be shown in the following table.

According to another embodiment of the present invention, a computer-readable recording medium having recorded thereon a program for executing one of the above methods is included.

In the overmodulation control apparatus for a three-phase voltage PWM inverter according to another embodiment of the present invention, a three-phase AC power is input to a switching element through an inductor, and the switching element is a feedback signal of a feedback controller using a signal of a DC terminal. A three-phase voltage type PWM inverter that is turned on / off according to the present invention and converts AC power into DC power, a command voltage vector converting unit generating a command voltage for controlling switching of the switching element and converting the command voltage into a space vector; A spatial vector display unit for displaying a spatial vector of the reference voltage in a basic vector model on a dq plane, which is expressed in a hexagonal shape and includes six effective vectors facing six vertices from the center, and the magnitude of the fundamental wave component of the phase voltage. A modulation index generator for obtaining a modulation index (m) using the magnitude of the fundamental wave component of the command voltage; (D) an overmodulation region determiner that determines a first overmodulated region and a second overmodulated region, and the first overmodulated region, boosting the magnitude of the command voltage to a first reference voltage vector, When a vector deviates from the basic vector model, a new switching time of two effective vectors adjacent to the command voltage is calculated by the same phase overmodulation technique, and if the second overmodulation area is the second overmodulation area, the magnitude of the command voltage is based on the second reference. and by the step-up in voltage vector, calculating a respective maintenance (α _h) according to the respective holding (α _h) it includes the modulation control for calculating the interval for projecting the primary vector model.

As described above, according to the present invention, the output voltage is linearized in the overmodulation region of the space vector PWM to maximize the voltage utilization rate of the SVPWM inverter. In addition, the overmodulation technique according to the present invention is easy to implement by using only the magnitude of the voltage in the first overmodulation region and the holding angle in the second overmodulation region according to the modulation index. This has the advantage that no complicated operation such as trigonometric operation is required.

FIG. 1A is a circuit diagram of a three-phase voltage PWM inverter, and FIG. 1B is a signal waveform diagram when overmodulation occurs.
1C is a diagram for describing a method of generating a space vector according to an operation of a three-phase voltage type PWM inverter.
2A and 2B are diagrams for explaining a process of generating a command voltage.
3 is a diagram for explaining a command voltage vector when an overmodulation phenomenon occurs.
4 is a diagram for describing a process of generating a voltage in a first overmodulation area according to a first embodiment of the present invention.
5 is a diagram illustrating a PWM overmodulation device according to an embodiment of the present invention.
6 is a flowchart illustrating a PWM overmodulation method according to an embodiment of the present invention.
7 is a view for explaining a process of generating a voltage in the first over-modulation region according to a second embodiment of the present invention.
8 is a diagram for describing an in-phase overmodulation scheme according to an embodiment of the present invention.
9 is a graph illustrating a relationship between m _v1 and m _v2 in a first overmodulation area according to a second embodiment of the present invention.
10 illustrates a conceptual diagram of voltage generation in a second overmodulation region according to an embodiment of the present invention.
11 is a graph showing a relationship between a modulation index m and a holding angle α _h in the second overmodulation area according to the second embodiment of the present invention.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

Hereinafter, the overmodulation phenomenon in the PWM inverter will be described.

FIG. 1A is a circuit diagram of a three-phase voltage PWM inverter, and FIG. 1B is a signal waveform diagram when overmodulation occurs.

According to the three-phase voltage-type PWM inverter as shown in Figure 1a, three-phase AC power (v _an , v _bn , v _cn ) is input to the switching element (S _a , S _b , S _c ) through an inductor, the switching element (S _a , S _b , S _c ) is turned on / off according to the feedback signal using the signal of the DC terminal to convert AC power to DC power. As shown in FIG. 1B, an overmodulation phenomenon occurs in a section in which the command voltage V _r is higher than the peak value V _c of the carrier, and in this section, the switching operation of the switching elements _Sa , S _b , and S _c occurs. This does not happen.

1C is a diagram for describing a method of generating a space vector according to an operation of a three-phase voltage type PWM inverter. In particular, FIG. 1C shows a spatial vector obtained by d-q conversion of a load phase voltage in a three-phase voltage PWM inverter in a basic vector model represented by a hexagon.

The basic vector model on the dq plane is represented by a hexagon, as shown in Fig. 1c, and centers the six effective vectors (V ₁ , V ₂ , V ₃ , V ₄ , V ₅ , V ₆ ) from the center to six vertices. It includes two valid vectors (V ₀ , V ₇ ). And the command voltage can be generated using two adjacent effective vectors.

Switching elements (S _a, S _b) in as shown in Figure 1c, for example in order to produce a V ₂ space vector 110, switching elements (S _a, S _b, S _c) shown in Fig. 1a is turned on, and the switching element (S _c) is turned off.

2A and 2B are diagrams for explaining a process of generating a command voltage. In particular, FIG. 2A illustrates a process for generating a command voltage V ^* located between the V ₁ space vector 100 and the V ₂ space vector 110, and FIG. 2B illustrates a proximity vector adjacent to the command voltage V ^* . (V ₁ , V ₂ ) is shown enlarged.

As shown in FIG. 2B, the proximity vectors V ₁ and V ₂ adjacent to the command voltage V ^* consume switching time of T ₁ and T ₂ , respectively, among the total switching time T _S.

The vector V _ref with respect to the command voltage V ^* may be expressed by Equation 1 below.

In addition, when the switching period is short, the magnitude of the command voltage V ^* is constant, and thus Equation 1 may be expressed as Equation 2 below.

3 is a diagram for explaining a command voltage vector when an overmodulation phenomenon occurs. That is, FIG. 3 is a space vector, which is a vector connecting the origin of the dq plane with the change of the three-phase variable. When an overmodulation occurs, the command voltage (V ^* ) is out of a hexagon. It is not possible to generate the reference voltage by combining the dog proximity vectors.

보다 큰 경우, 즉 육각형 내접원을 벗어날 경우 동특성(Dynamic response)의 향상을 위해 육각형의 빗면으로 지령 전압 벡터를 수정하는 것으로 전동기 벡터 제어 기법 등에 적용된다. 이에 비하여 정적 과변조 기법은 인버터 출력전압의 이용률을 최대화하기 위하여 V/F제어 등에서 선형제어 영역에서 6 스텝 제어 영역 등으로 자연스럽게 천이하도록 하는 과변조 방법이다. 따라서, 정적 과변조 기법은 과변조 영역에서 지령치 전압 벡터의 크기 및 위상을 조절하여 지령전압 벡터의 크기가 한 주기 동안의 평균전압이 동일하도록 지령치를 조정하는 기법으로, 변조지수 m의 크기에 따라 과변조 영역을 제1 과변조 영역(0.907 < m < 0.9514)과 제2 과변조 영역(0.9514 < m < 1)으로 나눌 수 있다. Therefore, in order to extend the output voltage of the inverter to a linear region or more, an overmodulation control method is required. Overmodulation control methods can be classified into static overmodulation and dynamic overmodulation. In dynamic overmodulation technique, the command voltage required in the transient state such as load or speed change is shown in FIG.

If larger, that is, out of the hexagonal inscribed circle, the command voltage vector is modified by the hexagonal inclined plane to improve the dynamic response. On the other hand, the static overmodulation technique is an overmodulation scheme that allows a natural transition from a linear control region to a six step control region in V / F control, etc. in order to maximize the utilization of the inverter output voltage. Therefore, the static overmodulation technique is a technique of adjusting the setpoint so that the magnitude of the setpoint voltage vector is equal to the average voltage for one period by adjusting the magnitude and phase of the setpoint voltage vector in the overmodulation region. The overmodulation area may be divided into a first overmodulation area (0.907 <m <0.9514) and a second overmodulation area (0.9514 <m <1).

Hereinafter, a method of controlling spatial voltage PWM overmodulation according to a first embodiment of the present invention will be described with reference to FIG. 4.

4 is a diagram for describing a process of generating a voltage in a first overmodulation area according to a first embodiment of the present invention.

First, the modulation index m can be expressed as Equation 3 below.

이다. Here, the command voltage V ₁ ^* represents the magnitude of the fundamental wave component of the command voltage. When six step driving, that is, square wave driving, m = 1, and V ₁ ^* is the fundamental wave size of the phase voltage corresponding to square wave driving.

to be.

의 경우이며, 이때의 변조 지수 m은 수학식 4를 통해 계산하면 0.907의 값을 가지게 된다. The starting point of the first overmodulation region is the point where the setpoint vector is in contact with the quadrilateral of the hexagon, and the setpoint voltage V ₁ ^*

In this case, the modulation index m has a value of 0.907 when calculated through Equation 4.

As shown in FIG. 4, the first overmodulation region is a region that compensates for a voltage drop in the region other than that where the overmodulation occurs, that is, the region where the command voltage is out of the hexagon by boosting the current command voltage. The end of the first overmodulation region is a case where the intersection angle between the setpoint voltage indicated by α _c and the hypotenuse becomes 0 when m = 0.9514.

In the first overmodulation region, the voltage is generated to be used to boost the voltage up to the region B capable of overmodulation, and to move along the hexagonal oblique surface for more values. Therefore, during the BC period, the voltage made smaller than the command voltage V ^* is boosted in the sections AB and CD that are capable of boosting, and the magnitude of the voltage vector is adjusted so that the average voltage matches the command voltage level. That is, in the first overmodulation region, the phase command remains unchanged and the voltage command uses an increased value.

In other words, in the A-B section, the boosted voltage is generated before inscribed with the hexagonal slope, and in the B-C section, the command value of the limited voltage is used in the hexagon, and the boosted voltage is generated again in the C-D section.

Here, the command value of the voltage may be represented by Equation 5 below.

The second overmodulation region starts at a point where the desired command voltage magnitude is not satisfied by stepping up the command voltage. That is, the second overmodulation region includes a region from the first overmodulation region to six-step operation. In the second overmodulation region, when the equivalent voltage control is performed, the magnitude and phase of the instantaneous voltage cannot be maintained and the magnitude and phase of the voltage vector must be adjusted.

Therefore, in the second overmodulation region, the setpoint voltage level is satisfied by staying at the largest vectors V ₁ and V ₂ for a predetermined time in order to satisfy the basic value of the given command voltage.

The voltage command in the second overmodulation area is expressed by the following equation (6).

Then, the magnitude of the voltage is determined according to the modulation index m. The output voltage is adjusted by adjusting the dwell time at the vertex of the largest output voltage. At this time, the holding time is determined by the holding angle α _h . The phase command is shown in Equation 7 below.

보다 작은 위상각 영역에서는 새로운 위상(α_v)는 수학식 7의 두 번째 식과 같이 새로운 위상 지령으로 설정된다.In the second overmodulation region, a phase command change occurs, and when V ^* is located in a region smaller than α _h , the voltage command value outputs a right vector, which is a vertex of the lower right side of the triangle, as in the first equation (7), and V ^* Is greater than the calculated holding angle (α _h )

In the smaller phase angle region, the new phase α _v is set to a new phase command as in the second equation of Equation 7.

보다 큰 경우에는 수학식 7의 세 번째 식과 같이 지령치 전압의 좌측에 있는 전압 벡터를 출력한다. Also, the phase of V ^*

If larger, the voltage vector on the left side of the setpoint voltage is output as shown in Equation 7 below.

However, according to the first exemplary embodiment of the present invention, it takes a long time and complicated implementation in that the voltage boosted according to the overmodulation region must be calculated separately. The following describes an overmodulation control technique that can be easily implemented.

Hereinafter, a PWM overmodulation device and a method thereof according to an embodiment of the present invention will be described with reference to FIGS. 5 and 6.

5 is a diagram illustrating a PWM overmodulation device according to an embodiment of the present invention. As shown in FIG. 5, the PWM overmodulation device according to an embodiment of the present invention includes a three-phase voltage type PWM inverter 510, a command voltage vector converter 520, a space vector display 530, a modulation index generator 540, The overmodulation area determiner 550 and the overmodulation control unit 560 are included.

First, the three-phase voltage PWM inverter 510 is a three-phase AC power is input to the switching element through the inductor as shown in Figure 1a, the switching element is turned on / off according to the feedback signal of the feedback control unit using a signal of the DC terminal AC Convert power to DC power.

The command voltage vector converter 520 generates a command voltage for controlling switching of the switching element and converts the command voltage into a space vector.

The space vector display unit 530 displays the space vector of the command voltage in the basic vector model on the d-q plane shown in FIG. 1C.

The modulation index generator 540 calculates the modulation index m using the magnitude of the fundamental wave component of the phase voltage and the magnitude of the fundamental wave component of the command voltage. The overmodulation area determiner 550 determines the first overmodulation area and the second overmodulation area according to the magnitude of the modulation index.

The overmodulation control unit 560 boosts the magnitude of the command voltage to a first reference voltage vector in the first overmodulation area, and when the first reference voltage vector deviates from the basic vector model, Calculate the new switching time of two valid vectors adjacent to the reference voltage. Then, in the second overmodulation region, the magnitude of the command voltage is boosted to the second reference voltage vector, the holding angle α _h is calculated, and the interval for projecting the base vector model according to the holding angle α _h is calculated. . Then, the switching signal is fed back to the three-phase voltage-type PWM inverter 510 to adjust the switching or duty ratio of the switching element included in the three-phase voltage-type PWM inverter 510.

FIG. 6 is a flowchart illustrating a PWM overmodulation method according to an exemplary embodiment of the present invention, and FIG. 7 is a diagram illustrating a process of generating a voltage in a first overmodulation region according to a second embodiment of the present invention. 8 is a diagram for describing an in-phase overmodulation scheme according to an embodiment of the present invention.

First, the command voltage vector converter 520 adjusts the command voltage V ^* for controlling the switching of the switching elements _Sa , S _b , S _c by using a DC voltage output from a three-phase voltage PWM inverter. In operation S610, the generated command voltage V ^* is converted into a space vector, which is a vector connecting the origin of the dq plane as illustrated in FIG. 3 (S620).

Next, the modulation index generator 540 obtains the modulation index m through Equation 3, and the overmodulation region determiner 550 determines the overmodulation region according to m (S630). That is, as described above, when the modulation index m falls within the range of 0.907 <m <0.9514, the first overmodulation area is determined. When the modulation index m falls within the range of 0.9514 <m <1, the second overmodulation area is determined.

If it is determined as the first overmodulation region, in the first overmodulation region, the fundamental voltage component of the command voltage (V ^* ) value has a new command voltage, that is, the command value voltage when the stepped-up voltage value moves in the locus of a circle as shown in FIG. It generates a voltage boosted to match the fundamental wave size of. The magnitude of the voltage boosted here is calculated by Fourier series expansion. For convenience, Equation 5 is again represented by Equation 9, and in Equations 8 and 9, V ₂ represents the magnitude of the boosted voltage, and V ₁ represents the peak value of the fundamental wave of the setpoint voltage.

In order to implement a static overmodulation technique in the first overmodulation region by applying the in-phase overmodulation technique, only V _2, which is the magnitude of the boosted voltage, needs to be determined. That is, in Equation 9, since the voltage vector represented by V ₂ e ^{j θ} is projected on the hypotenuse as in the second equation of Equation 9 in the period α _c <θ <π / 3-α _c , the same phase overmodulation technique is used. When the setpoint voltage is determined in the period α _c <θ <π / 3-α _c , the second equation of Equation 9 is satisfied by itself, because V ₂ e ^{j θ} is projected on the hypotenuse of the hexagon. On the other hand, in the period α _c <θ <π / 3-α _c , since the condition is T1 + T2> Ts, a voltage command value satisfying Equation 9 can be generated by the condition T1 + T2> Ts without information on α _c .

Here, the magnitude of V ₂ may be determined such that the magnitude of V _{1, which} is the magnitude of the initial setpoint voltage given by m, and the magnitude of the voltage generated by Equation 9 are the same. Determine the size to match. The equation for this is shown in Equation 10.

The coefficients to be multiplied according to the period during the Fourier coefficient calculation are represented by the same value in both terms of the equation, and are removed for the convenience of calculation.

임을 이용하여, 수학식 10에 대입하여 정리하면 다음의 수학식 11를 얻을 수 있다.And,

By substituting and substituting into Equation 10, Equation 11 can be obtained.

로 하여 위의 식을 정리하면 아래의 수학식 12 및 수학식 13과 같이 나타낼 수 있다.here

The above equations can be summarized as in Equations 12 and 13 below.

Here, by substituting Equation 13 into Equation 12, the relationship between α _c , which is an angle corresponding to point B in FIG. 4, and the command voltage can be obtained as in Equation 14.

Α _c is obtained from the magnitude of the command value voltage V ₁ in the second overmodulation region by using Equation 14, and substituting the obtained α _c into Equation 13, V ₂ can be obtained. In this manner, V ₂ , which is the magnitude of the voltage boosted by the magnitude of the command value voltage V ₁ , can be obtained from the modulation index m.

On the other hand, as shown in Figure 4, the new command voltage having the magnitude of V ₂ is moved along the trajectory of the circle in the AB and CD sections and along the slope of the hexagon in the BC section. As shown in the figure, the new command voltage stays on the hexagonal oblique surface to generate a voltage boosted to V _b ^* .

Here, the same phase overmodulation technique according to the embodiment of the present invention will be described with reference to FIG. 8. In the same phase overmodulation technique, when the command vector is out of the hexagon, the phase of the command voltage is projected to the hypotenuse of the hexagon. Create a new vector as the setpoint voltage by (V ^* -> V _new ^* ).

The new application time T ₁ ^new , T ₂ ^new to generate the projected voltage V _new ^{* at} this time is determined as in Equation 15 below. The overmodulation technique according to the embodiment of the present invention is applied to the first overmodulation region and the second overmodulation region in the same manner to calculate the switching time.

Here, T ₁ represents the first switching time of two adjacent effective vectors V ₁ and V ₂ for generating the command voltage V ^* , and T _S represents the total switching application time.

That is, the controller 530 calculates T ₁ and T _{2 based} on the boosted voltage without distinguishing sections, and when T ₁ + T ₂ > T _S , a new application time T ₁ ^new , T as shown in Equation 5 ₂ ^new ), and the overmodulation technique can be simply implemented without distinguishing a section such as a BC section in the first overmodulation region (S640). In Equation 14, the relationship between V ₂ (= V _b ^* ) according to V ₁ (= V ^* ) may be represented as shown in FIG. 7.

Therefore, the linearized equation is linearly used for each section according to V ₁ , that is, according to the modulation index. FIG. 7 is a display of FIG. 4 again, and the relationship between V ₁ (= V ^* ) and V ₂ (= V _b ^* ) is shown again to represent the relationship between modulation index m.

이고 이때 변조 지수 m은 0.907이다. 이때 V₂를 나타내는 승압된 변조지수 m_v2는 0.907이 된다. 제1 과변조 영역에서는 m_v2는 m_v1에 비해 커지게 된다. Meanwhile, the size of V ₁ at the start point of the overmodulation area is

And the modulation index m is 0.907. In this case, the boosted modulation index m _v2 indicating V ₂ is 0.907. In the first overmodulation region, m _v2 becomes larger than m _v1 .

Here, m _v2 is defined in the present invention as in Equation (13), and Equation (17) is a representation of the modulation index m to facilitate the comparison with Equation (16). V _inst ^* in Equation 16 is the instantaneous value of the command voltage, and is distinguished from the peak value of the fundamental wave size indicated by V ^* .

At the end of the first overmodulation region, V ₁ is 0.6057V _dc, where m _v1 is 0.9514 and m _v2 is 1.0472, which means that the magnitude of the boosted voltage is the voltage magnitude circumscribed to the hexagon. The value corresponds to 3V _dc . Accordingly, when m _v2 according to m is drawn using Equation 3, Equation 13, and Equation 14, FIG.

9 is a graph illustrating a relationship between m _v1 and m _v2 in a first overmodulation area according to a second embodiment of the present invention. If the relationship between m _v1 and m _v2 according to FIG. 9 is approximated in three sections using the curve fitting tool of Matlab, it can be summarized as shown in Table 1. Table 1 shows an approximation equation of the modulation index in the first overmodulation region.

Here, in the equation m, it can be seen that m divided by 4 / π * V _dc / 2 = 2 / π * V _dc , so m or m _v1 is the reference voltage of the original setpoint (base wave voltage). Value). Therefore, since the command voltage can be converted into m by Equation 4, the magnitude of the boosted reference voltage according to the magnitude of the command voltage can be inferred from Table 1.

On the other hand, since m _v2 is 1.0472, that is, the output voltage can no longer increase after the point at which the boosted voltage becomes 2 / 3V _dc , the mode must be switched to the second overmodulation region. In order to satisfy the fundamental wave magnitude of the setpoint voltage in the second overmodulation region, as shown in Equation 7, 2 / 3V _dc during the holding angle α _h . The section for applying the voltage of is required.

As in the first overmodulation region, a new voltage command is generated in the second overmodulation region using the in-phase overmodulation technique (S650).

인 경우보다 큰 경우에는 60도에서 머물게 하며 (도 10의 (c)), 이 외의 구간 (도 10의 (b)) 에서는 지령 위상각과 일치하도록 전압벡터를 생성한다. 10 illustrates a conceptual diagram of voltage generation in a second overmodulation region according to an embodiment of the present invention. In other words, if the trajectory of the setpoint voltage is the inner semicircle indicated by the scale line, the size of the stepped-up voltage is fixed to 2 / 3V _dc and only the holding angle (α _h ) is calculated. The phase of the voltage vector remains at 0 degrees (Fig. 10 (a)), and the current phase angle

If larger than, stay at 60 degrees (Fig. 10 (c)), and in other sections (Fig. 10 (b)) generates a voltage vector to match the command phase angle.

The new command voltage V _new ^* and the new phase angle command value θ ^* in the second overmodulation region shown in FIG. 10 are generated as in Equation 18.

Calculation of the holding angle α _h according to the modulation index m, that is, the equivalent value of V ₁ can be obtained as follows. The holding angle α _h is obtained by the same method as that of the first overmodulation region, and the equation (19) can be obtained by performing Fourier series expansion to equalize the fundamental wave voltage magnitude of the setpoint voltage and the setpoint voltage using Equation 5. have.

Equation 19 is developed as shown in Equation 20. If the equation is divided into a real part and an imaginary part, Equation 21 can be obtained.

Here, when Equation 21 is arranged using the modulation index m of Equation 3, the relationship between the modulation index m and the holding angle α _h can be expressed by Equation 22 below.

Therefore, it can be seen that the holding angle α _h obtained by using Equation 22 from the magnitude of the first setpoint voltage is equivalent to m, as shown in FIG. 11.

11 is a graph showing a relationship between a modulation index m and a holding angle α _h in the second overmodulation area according to the second embodiment of the present invention.

As in the first over-modulation region, using the Matlab curve fitting tool, it is divided into three sections and the approximation of the holding angle (α _h ) according to the modulation index (m) to the linear equation is shown in Table 2 below. have. Table 2 shows the modulation index approximation equation in the second overmodulation region.

As described above, according to the exemplary embodiment of the present invention, the switching time calculation in the second overmodulation region is determined according to the voltage phase and magnitude. That is, the phase of the setpoint voltage is determined by the approximation equation shown in Table 2, and the magnitude of the holding angle α _h according to the modulation index m is determined by using Equation 18. On the other hand, the instantaneous magnitude of the new setpoint voltage is 2 / 3V _dc . In the second overmodulation region, the setpoint voltage magnitude is 2 / 3V _{dc, which} is always outside the hexagonal quadrilateral, that is, T _1. + T ₂ > T _S , the new application time projected on the quadrangle is determined by Equation 15, which is an in-phase modulation technique.

In operation S660, the switching time is calculated using the ratio of the ratio for generating the PWM. That is, the switching time is calculated by calculating the switching time according to the ratio of time of the in-phase overmodulation scheme, that is, through the duty ratio.

Since it is necessary to examine the relationship between m _v1 and m _{v2 in} the overmodulation region, Equations 16 and 17 are represented by Equations 23 and 24.

In Equation 23, the modulation index m represents the ratio of the fundamental wave voltage magnitude and the fundamental wave size of the command value when the square wave is driven. When the range of m is changed from 0 to 1 in the V / F control in the overmodulation area, 1 corresponds to square wave driving, where the setpoint voltage corresponds to 2 / 3V _dc and the holding angle α _h corresponds to 30 °. . Since the magnitude of the voltage boosted in the overmodulation region is not an elementary wave component but an instantaneous value, it is necessary to determine the boosted voltage using the instantaneous value when implementing the proposed technique. Therefore, the modulation index using the instantaneous value is m _v2 and is defined as Equation 25.

V ₁ ^* is the magnitude of the fundamental wave of the setpoint voltage, and V _inst ^* is the instantaneous value of the setpoint voltage. If the fundamental wave of V ^* corresponding to square wave driving is 2V _dc / π, V _inst ^* becomes 2 / 3V _dc and m _v2 = 1 but m _v2 = π / 3 = 1.0472 Thus, the value of m _v1 equal to m ranges from 0 to 1, whereas m _v2 has a value from 0 to 1.0472. Since the setpoint voltage is instantaneous, the voltage vector application times T _{1 ,} T _{2 and} T ₀ are generated using m _v2 .

As described above, according to the exemplary embodiment of the present invention, the output voltage may be linearized in the overmodulation region of the SVPWM to maximize the voltage utilization rate of the SVPWM inverter. That is, according to an embodiment of the present invention to improve the complicated operation in the generation of the over-modulation voltage and the generation of the setpoint voltage to increase the output linearity of the setpoint voltage in the static overmodulation technique such as V / F control of the induction motor For this purpose, a new static overmodulation scheme using the in-phase overmodulation scheme, which is used in the vector control technique, is proposed.

The overmodulation technique according to the embodiment of the present invention is easy to implement by using only the magnitude of the voltage in the first overmodulation region and only the holding angle in the second overmodulation region according to the modulation index. The advantage of generating complex calculations such as trigonometric calculations is not required.

Embodiments of the present invention include a computer-readable medium having program instructions for performing various computer-implemented operations. This medium records a program for executing the overmodulation control method of the three-phase voltage-type PWM inverter described so far. The medium may include program instructions, data files, data structures, etc., alone or in combination. Examples of such media include magnetic media such as hard disks, floppy disks and magnetic tape, optical recording media such as CD and DVD, programmed instructions such as floptical disk and magneto-optical media, ROM, RAM, And a hardware device configured to store and execute the program. Or such medium may be a transmission medium, such as optical or metal lines, waveguides, etc., including a carrier wave that transmits a signal specifying a program command, data structure, or the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

Claims (17)

Three-phase AC power is input to the switching element through an inductor, and the switching element is turned on / off according to the feedback signal of the feedback control unit using the signal of the DC terminal to convert the AC power into DC power. In the modulation control method,
Generating a command voltage for adjusting the switching of the switching element and converting the command voltage into a space vector;
Displaying the spatial vector of the command voltage in a basic vector model on the dq plane, which is expressed in the form of a hexagon and includes six effective vectors facing six vertices from the center,
Obtaining a modulation index (m) using the magnitude of the fundamental wave component of the phase voltage and the magnitude of the fundamental wave component of the command voltage;
Determining a first overmodulation region and a second overmodulation region according to the magnitude of the modulation index;
In the first over-modulation region, the command voltage is boosted to a first reference voltage vector, and when the first reference voltage vector is out of the basic vector model, 2 adjacent to the command voltage by an in-phase overmodulation technique is used. Calculating a new switching time of the effective vectors,
Wherein the section of the projection to the base vector model in accordance with a second and if the modulation region, and the step-up the magnitude of the command voltage to a second reference voltage vector, the holding angle (α _h) of the holding by calculating each (α _h) The overmodulation control method of the three-phase voltage-type PWM inverter comprising the step of calculating. The method of claim 1,
Obtaining the modulation index (m) is,
The overmodulation control method of the three-phase voltage PWM inverter obtained by the following equation:

Here, the command voltage (V ₁ ^* ) represents the magnitude of the fundamental wave component of the command voltage,

Denotes the magnitude of the fundamental wave component of the phase voltage. The method of claim 2,
Determining the first overmodulation area and the second overmodulation area,
A three-phase voltage PWM inverter configured to determine the first overmodulation region when the modulation index m falls within a range of 0.907 <m <0.9514, and determines the second overmodulation region when within a range of 0.9514 <m <1. Overmodulation control method. The method of claim 3,
An overmodulation control method of a three-phase voltage type PWM inverter for boosting the magnitude of the command voltage to the first reference voltage vector through the following equation in the first overmodulation region:

Here, V ₁ represents the magnitude of the command voltage, V ₂ represents the magnitude of the boosted first reference voltage,

Represents the height of the basic vector model, and α _c represents the angle between the point where the first reference voltage intersects the basic vector model and the neighboring vertex of the hexagon. The method of claim 4, wherein
The magnitude of the first reference voltage according to the magnitude of the command voltage is calculated using the following table.

The method of claim 5,
Calculating the new switching time,
The new switching time (T ₁ ^new , T ₂ ^new ) for generating the first reference voltage vector is an overmodulation control method of a three-phase voltage PWM inverter represented by the following equation:

Here, T ₁ and T ₂ represent the first switching time of two valid vectors adjacent to the command voltage for generating the command voltage, and T _S represents the total switching application time. The method of claim 6,
The magnitude of the second reference voltage is fixed to 2 / 3V _dc , the phase of the second reference voltage according to the phase of the command voltage is overmodulation control method of the voltage-type PWM inverter is set as follows:

Here, θ 'is the phase of the second reference voltage (V _new ^* ), θ is the phase of the command voltage, α _h means the holding angle of the second reference voltage. The method of claim 7, wherein
The holding angle (α _h ) according to the modulation index (m) in the second overmodulation region is shown in the following table.

A computer-readable recording medium having recorded thereon a program for causing a computer to execute one of the methods recorded in claims 1 to 8. Three-phase AC power is input to the switching element through the inductor, the switching element is turned on / off in accordance with the feedback signal of the feedback control unit using a signal of the DC terminal three-phase voltage PWM inverter for converting the AC power to DC power,
A command voltage vector converting unit generating a command voltage for controlling switching of the switching element and converting the command voltage into a space vector;
A space vector display unit displaying a space vector of the command voltage in a basic vector model on a dq plane, which is expressed in the form of a hexagon and includes six effective vectors facing six vertices from the center;
A modulation index generator for obtaining a modulation index (m) using the magnitude of the fundamental wave component of the phase voltage and the magnitude of the fundamental wave component of the command voltage,
An overmodulation region determiner for determining a first overmodulation region and a second overmodulation region according to the magnitude of the modulation index, and
In the first over-modulation region, the command voltage is boosted to a first reference voltage vector, and when the first reference voltage vector is out of the basic vector model, 2 adjacent to the command voltage by an in-phase overmodulation technique is used. Calculate a new switching time of two effective vectors, and if the second overmodulation region, the magnitude of the command voltage is boosted to a second reference voltage vector, and the holding angle α _h is calculated to calculate the holding angle α _h . And an overmodulation control unit for calculating a section projected onto the basic vector model. The method of claim 10,
The modulation index generator,
An overmodulation control device for a three-phase voltage PWM inverter obtained by the following equation:

Here, the command voltage (V ₁ ^* ) represents the magnitude of the fundamental wave component of the command voltage,

Denotes the magnitude of the fundamental wave component of the phase voltage. The method of claim 11,
The overmodulation area determiner,
A three-phase voltage PWM inverter configured to determine the first overmodulation region when the modulation index m falls within a range of 0.907 <m <0.9514, and determines the second overmodulation region when within a range of 0.9514 <m <1. Overmodulation control device. The method of claim 12,
An overmodulation control device for a three-phase voltage type PWM inverter for boosting the magnitude of the command voltage to the first reference voltage vector through the following equation in the first overmodulation region:

Here, V ₁ represents the magnitude of the command voltage, V ₂ represents the magnitude of the boosted first reference voltage,

Represents the height of the basic vector model, and α _c represents the angle between the point where the first reference voltage intersects the basic vector model and the neighboring vertex of the hexagon. The method of claim 13,
The magnitude of the first reference voltage according to the magnitude of the command voltage is an overmodulation control device of a three-phase voltage-type PWM inverter is obtained using the following table.

15. The method of claim 14,
The overmodulation control unit,
The new switching time (T ₁ ^new , T ₂ ^new ) for generating the first reference voltage vector is an overmodulation control device of a three-phase voltage PWM inverter represented by the following equation:

Here, T ₁ and T ₂ represent the first switching time of two valid vectors adjacent to the command voltage for generating the command voltage, and T _S represents the total switching application time. 16. The method of claim 15,
The magnitude of the second reference voltage is fixed to 2 / 3V _dc , the phase of the second reference voltage according to the phase of the command voltage is an over-modulation control device of a voltage-type PWM inverter is set as follows:

Here, θ 'is the phase of the second reference voltage (V _new ^* ), θ is the phase of the command voltage, α _h means the holding angle of the second reference voltage. The method of claim 16,
The holding angle (α _h ) according to the modulation index (m) in the second overmodulation region is shown in the following table.

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